1. Field of the Invention
This invention relates generally to the geometric layout for the light emitting diodes of a line exposure array and, more particularly, to a line exposure array of light emitting diodes geometrically configured to line scan and uniformly expose a photosensitive material.
2. Description of the Prior Art
Electronic image recording apparatus of a type comprising a line exposure array stationed in light exposing relationship to a photosensitive material and comprising a plurality of linearly spaced apart light emitting diodes are well known in the art. Means are generally provided for effecting a relative displacement between the light exposure array and the photosensitive material in a direction transverse to the longitudinal axis of the exposure array so as to affect an exposure of the entire surface of the photosensitive material.
Line exposure arrays of the aforementioned type comprising a plurality of light emitting diodes aligned in spaced apart relation along the longitudinal axis thereof generally provide for a nonuniform line exposure as a result of those portions of the photosensitive material immediately opposite the areas between the light emitting diodes receiving substantially less exposure than those areas of the photosensitive material immediately opposite the light emitting diodes. This nonuniform line exposure results in visible underexposed stripes extending across the photosensitive material in the direction of relative displacement between the photosensitive material and the line exposure array. The visibility of such stripes can be reduced but not entirely eliminated by minimizing the spacing between the light emitting diodes. The degree to which the spacing between the light emitting diodes can be minimized, however, is limited by practical constraints since adjacent light emitting diodes must also be insulated from each other. This insulation requirement results in a minimum degree of spacing between the light emitting diodes being required thereby making it impossible to entirely eliminate some minimum degree of spacing between the diodes. In addition, as the spacing between the light emitting diodes is decreased, the light intensity at the adjacent edges of the diodes tends to roll off and create in effect adjacent dead zones. Such dead zones also operate to underexpose those regions of the photosensitive material immediately adjacent thereto. The dead zones could be eliminated by using lenses to defocus the light emitting diodes; however, such an approach leads to unnecessary picture blurring and inefficient use of the brightness available from the light emitting diodes.
Other methods for eliminating the underexposed stripes resulting from the spaced apart light emitting diode configuration of a line exposure array have involved mechanical mechanisms for vibrating or oscillating the line exposure arrays in directions parallel to the longitudinal axis of the line exposure array. Such oscillations are generally limited to moving each light emitting diode a limited distance equivalent to the distances between which the light emitting diodes are spaced apart. While such systems can satisfactorily provide a uniform line exposure from a linear array of spaced apart light emitting diodes, there is added a substantial degree of mechanical complexity, cost and size with an attendant decrease in reliability.
Therefore, it is a primary object of this invention to provide a line exposure array of spaced apart light emitting diodes geometrically configured to uniformly expose the photosensitive material without mechanical vibration and its attendant complexity and cost.
Other objects of the invention will be in part obvious and will in part appear hereinafter. The invention accordingly comprises a mechanism and system possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure.